I think (on paper) this might be one of the best squads. It is Verena, Murne, Diala, and Mak.

Range: Mak is a long range sniper. Murne has medium range (although from my experience, she doesn't attack much). Diala is Melee. Verena is Close Range. There is a good amount of diversity here.

Attributes: Strength Focus (eyeball thing) Tech

Mak: Medium Medium Strong

Verena: Medium Medium Medium

Murne: Weak Strong Medium

Diala: Medium Strong Weak

There is a hero who is strong in each Skill except Strength where 3 characters are Medium.

Defense: Two Whites, Two Blacks. Pretty Balanced

Speed: All are 4. Could be a weakness.

Endurance: Three are 5. One is 4. This definitely helps with the Speed 4.

Support Abilities: Murne has lots. Diala has some good ones too.

Thoughts?

There is a thread on this very page, just a few posts down from yours right now, where this is being talked about.

https://community.fantasyflightgames.com/topic/227137-which-one-is-the-best-4-heroes-group/

Replace Diala with Gaarkhan to round out your attributes and replace Verena with Jyn so she's not competing with Gaarkhan as the close range brawler.